A directory with a hyphen currently generates an InvalidId error because
of the regex in libcontainer. I don't believe there is any reason a
hyphen should be disallowed.
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
Alexander Morozov
Phil Estes
Michael Crosby